SAMPE Journal - March/April 2024 - 34

FEATURE / THERMAL PROTECTION SYSTEMS MATERIALS
calipers[26]
. Figure 21 shows the photogrammetry
experimental setup and a typical recession vs. time
of PICA when evaluated at 750 W/cm2
for 60s[26]
.
Figure 22 shows surface recession measurement
of Starfire CMC evaluated at 1,000 W/cm2[26]
. This
photogrammetry recession measurement system
has been demonstrated on a variety of ablators and
is now being adapted with the OTB aerothermal
testing routinely. This photogrammetry technique
provides in-situ recession rate with more accuracy
than our previous recession measurement
technique.
A.4 Schlieren Imaging Equipment (Newly
Installed Equipment))
ThorLabs 2 " diameter, 1,000 mm focal length
aluminum coated concave mirror on an optical
breadboard-mounted post approximately 8 "
behind the
torch flame
describes
Table 2. Recession rate comparison of a variety of ablatives[24]
.
the newly
installed Schlieren Imaging equipment. Mirror was
satisfactory for torch detail but too small to capture
where impinging flow travels past the sample.
Panasonic GH5 mk1 camera body with PanasonicLeica
100-400 mm lens (set at 400 mm focal length)
is used. Small LED flashlight with aluminum foil
cover punctured with a needle to serve as the
light source. No knife edge is required due to the
exceedingly small amount of light arriving at the
camera sensor using f/22, 1/16,000 s shutter speed
(electronic shutter), ISO 100. Figure 23 shows
Schlieren imaging equipment demonstration using
heat flux from 150 to 1,500 W/cm2
of oxyacetylene
flame impinging on an OTB test model. Additional
research is in progress.
B. NASA HYMETS Arc Jet Testing
The HYMETS is an affordable state of the art (SOTA)
arc jet test facility at NASA Langley Research Center
(LRC) that can be used for further screening of TPS
materials after they are screened by the low-cost
and fast turnaround OTB test facility. Figure 24
zshows a brief description of the HYMETS facility[27]
.
HYMETS standard instrumentation includes
stagnation pressure, catalytic cold wall heat flux,
surface temperature, back face temperature, and
bulk enthalpy calculation. Data collected from arc
jet testing will be used for MR model validation
(Section VI Numerical Modeling).
V. Microstructures Characterization and
Modeling
The KRG team uses scanning electron microscopy
(SEM) as well as the Lawrence Berkeley National
Laboratory/Advanced Light Source Beamline
8.3.2 synchrotron hard X-ray micro-CT to examine
the microstructures of TPS materials[28]
. Figure 25
shows the SEM images of virgin PICA (left) and
char PICA (right). The phenolic resin in the char
PICA was pyrolyzed leaving the bare carbon fibers
behind.
Figure 21. Photogrammetry in-situ recession measurement system (left) and
visualization of recession vs. time of PICA evaluated under OTB at a heat flux of 750 W/
cm2
for 60s (right).
Figure 22. Surface recession measurement of Starfire CMC evaluated at 1,000 W/cm2
.
Figure 23. Schlieren imaging equipment demonstration using heat flux from 150 to
1,500 W/cm2
of oxyacetylene flame impinging on an OTB test model.
34 | SAMPE JOURNAL | MARCH APRIL 2024
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SAMPE Journal - March/April 2024

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